Behcet's disease is particularly prevalent in "Silk Route" populations, but it has a global distribution. The diagnosis of the disease is based on clinical criteria as there is as yet no pathognomonic test, and mucocutaneous lesions, which figure prominently in the presentation and diagnosis, may be considered the diagnostic hallmarks. Among the internationally accepted criteria, painful oral and genital ulcers, cutaneous vasculitic lesions and reactivity of the skin to needle prick or injection (the pathergy reaction) are considered hallmarks of Behcet's disease, and often precede other manifestations. Their recognition may permit earlier diagnosis and treatment, with salutary results. This paper describes the various lesions that constitute the syndrome and focuses on those that may be considered characteristic.